Lettuce is the 2nd most popular vegetable
in the US (second only to potato), and head lettuce is certainly the most
recognizable type. So, it is not uncommon for us to hear the question “Why
don’t you produce iceberg lettuce in the greenhouse?” There are, in fact, several key reasons
iceberg lettuce is not commonly grown in vegetable greenhouses in the United
States. They are listed below and loosely ranked by importance, but these
reasons may vary depending on production area and market.

1) Market potential and price

One of the most important reasons that we do not see
head lettuce in the greenhouse is because the economics of the market are not
always encouraging. Nearly all of US head lettuce is produced in California
(spring through fall) and Arizona (winter). Huge expanses of open field
production are dedicated to lettuce production in some of the most productive
cropping areas in the world. Soil and climate factors make these regions quite
appropriate for head lettuce production and the scale of production also contributes
to competitive advantages. For example, recent terminal market data reported
that head lettuce cartons (approximately two dozen 2 lb. heads of lettuce) are
selling for $11.00 to $17.00. These prices illustrate that greenhouse producers
are unlikely and unwilling to produce head lettuce at prices that could be
competitive with field production. An
additional facet to this topic of markets is that recent per capita consumption
of head lettuce has been flat or on the slight decline as other leafy vegetables
have become more popular.

Iceberg lettuce typical in California open
field production. Specific cultivars are
slotted in specific times of year for production regions of CA and AZ across
the entire year.

2) Production time

Typically in the open field, head lettuce matures in 70 to 80
days in the summer and up to 130 days in winter or lower light and temperature
seasons. Of course one of the benefits of greenhouse production is the
potential for faster growth rates and reduced production times. To date, in
summer greenhouse production in OH, we have harvested our iceberg lettuce
approximately 55 to 60 days after seeding. However, the total weight of our
lettuce may not equal field packed cartons. This production time contrasts with
a bibb production schedule in the greenhouse which might produce a crop in 40
to 50 days.

3) Nutrition

As consumers become conscious of the nutrient and
antioxidant levels in their food, they continue to become more discerning in
food purchases. Due to underlying genetics, plant growth form and a few other
factors, iceberg lettuce is not the most nutrient dense leafy green vegetable.
The table below (From USDA National Nutrient Database for Standard Reference
Release 24 ) gives average nutrient information for the most common types of
lettuce. Remember that these are averages from primarily soil grown crops from
around the country, so they do not represent the exact profile of product from
individual greenhouses or cultivars. Nevertheless, this table does support the
generally held perception that iceberg lettuce contains fewer nutrients per
serving that other lettuces and certainly other leafy greens. However, keep in
mind that iceberg lettuce from greenhouses has been less often evaluated than
that from the open field.

4)Customer Preference and
Perception

This potential reason for the lack of iceberg lettuce in US
greenhouses is linked with the nutrition topic discussed above. Most greenhouse
lettuce producers are growing and marketing their crop as a premium product.
This means that the quality of the crop is crucial, but the perception of the
crop is also important. Iceberg lettuce is often viewed by many discerning
consumers as inferior in taste, visual appeal, and nutrition to the bibb, romaine
and leaf lettuces. There is also little attraction based on novelty or
distinctiveness. These views mean that many of the most profitable potential
customers for hydroponic greenhouse producers may be less interested in iceberg
than other leafy crops. However, if greenhouse producers were able to market a
product with comparable attributes (crisp, multiple servings per head, etc) and
improved taste, freshness, or nutrition, these perceptions and preferences
could change.

5)Adaptability of cultivars
and environments

Much of greenhouse lettuce production (especially bibb)
utilizes cultivars that were specifically bred and developed for greenhouse
environments. These cultivars can generally be depended upon to perform
consistently across seasons and even geographic areas. When investigating types
of lettuce, like iceberg, that are less often produced in greenhouses,
preferable cultivars and knowledge of how they may perform is limited.

Additionally, iceberg lettuce often requires specific
environmental conditions to produce the tight head consumers are accustomed to-
without bolting or becoming bitter. So, even though we can control temperatures
closely in greenhouses, producers may not be able to exactly emulate conditions
that are common in field iceberg production. There may be more seasonal
constraints of light and temperature on iceberg production in many US
greenhouses than we experience in producing other types of lettuce.

So, why
would we be interested?

After spending the time to try and elucidate why iceberg is
rarely produced in hydroponic greenhouses, you are probably asking what would
possibly be the attraction. While I will be the first to admit that greenhouse
iceberg is unlikely to become a US market force in the near future, there are some
reasons for investigation.

First, familiarity is not always a negative. Some consumers
will always be attracted to what they know best and producers should always be
ready to fill small market niches if they are possible and profitable-
especially if they can provide a product with superior quality.

Secondly, we at CropKing deal with producers not only in the
US, but also internationally. Market demands and dynamics may differ
considerably in these areas. For instance, in the Caribbean islands where
imports are expensive and often of poor quality, iceberg may be both desired by
consumers and potentially profitable for greenhouse growers.

Thirdly, it is always important to investigate
potential crops and understand both the benefits and drawbacks to their
cultivation to assist current and future producers- essentially, we need to
have solid backing to the answers that we give growers.

About Us

CropKing has specialized in hydroponics and controlled environment agriculture for nearly 30 years. We have established ourselves as a leader in the industry and have helped numerous people become successful hydroponic farmers.

This blog was established to keep our growers up to date on the research we are doing here at CropKing. The research is being done by our horticulturist Dr. Natalie Bumgarner.